The electrodes of a battery are an electrically conductive anode and an electrically conductive cathode. Each has a layer of active material which can react with an electrolyte to either liberate or absorb electrons. When an electron is liberated at the interface of an active material and electrolyte it must travel through the active material and through the negative electrode, then through an external circuit to the positive electrode, and through another layer of active material where it is absorbed at the interface of the other active material with electrolyte. Each layer of material that electricity must travel through has a certain resistivity. The electrical resistance R of a layer is determined by equation 1.R=ρL/A  equation (1)
ρ is the resistivity of the material, L is the length electricity must travel through the material, and A is the cross section area of the path that electricity takes through the material. For a given material volume V the resistance is determined by equation 2.R=ρL2/V  equation (2)
Since the resistance of a given volume of material in a layer is proportional to the square of the electricity's path length through a material it is important to make the electrical path through the material with the highest resistivity as short as possible. Active materials often have a high resistivity and cause a high series resistance in a battery. [Lisjak et al., (1997), Megahed (1995), Samsonov (1982])
Prior art inventions use a paste to form a layer of active material between the metal electrode and the electrolyte [Bando et al. (1999), Bi et al. (1999), Nordlinder (2003) and Ghantous (2007)]. Typically, the layer of active material is between several hundred micrometers to over one millimeter thick and not fully dense. A battery with a thick layer of active material has a high electrical resistance through the active material and has low power. Some prior art batteries use fine powders or nano particles of active material to increase the surface area. However, if electrons or ions must travel through several particles of resistive material to reach the next layer of less resistive material the resistive path length is long and the resistance is high. A high-power battery must have a thin layer of active material and a high specific area to minimize the electrical path length and minimize the resistance. Thin film batteries have been used in prior art (Bates et al. (1994), Tipton et al. 1996) to obtain low series resistance; however, they have low cathode loadings (e.g., 0.013 mAh/cm2) or low energy per projected area. Prior art thin film batteries have not realized high volume fractions of active material and have low energy density. In practical non-thin-film batteries one desires much higher cathode loadings, e.g., one-thousand times larger.
For capacitive energy storage, electrodes have been developed with very high surface to volume ratio [Welsch and McGervey 2001 and 2002, G. P. Klein (1968), W. Mizushima et al. (1977), 1. Fife et al. (1993)] but such electrodes have not found use in batteries.
In the present invention we describe a new battery electrode that achieves the goal of lower series resistance and higher power than in prior art.